There have been conventionally air guns equipped with an air chamber that stores compressed gas from a compressed gas vessel and has a valve. In such an air gun, a bullet is fired off by hitting the valve with a hammer or a striker to release compressed gas.
There has also been the electric air gun (automatic electric air gun) disclosed in Japanese Unexamined Patent Publication No. Hei 3 (1991)-221793. This electric air gun is provided in its cylinder with a piston. In this electric air gun, the following takes place when its trigger is pulled: the cylinder is moved to compress the gaseous body in the cylinder and bullets are fired off by the pressure of this compressed gaseous body.
The electric air gun disclosed in Japanese Unexamined Patent Publication No. Hei 3 (1991)-221793 is equipped with a motor as a power source for moving the piston backward. The rotary power from the motor is transmitted to a sector gear through a large number of gears. The piston forms a rack. The sector gear linearly moves the piston backward to compress a piston spring. When the engagement between the sector gear and the rack is subsequently removed, the piston is moved forward by the biasing force of the spring to compress a gaseous body. A BB bullet is fired off by the pressure of the compressed gaseous body.
An air gun using a push-type solenoid as moving power for a striker for hitting the valve of a compressed gas vessel is also publicly known. In this air gun, the valve is opened by the movement of the moving core of the solenoid and the compressed gas in an air chamber is jetted out to fire off a BB bullet.
U.S. Pat. No. 5,531,210 discloses a toy gun using a rack and a pinion as a manual air gun. When a handle is manually pulled (cocking) in this air gun, the rack and the pinion are moved to compress a spring. When a trigger is pulled, the spring is decompressed. As a result, a piston advances to compress the air in the air gun and jets it out to fire off a cylindrical bullet.
U.S. Pat. No. 6,418,919 discloses a technique for using a motor to shake a bullet feed hopper and thereby letting a large number of bullets in the hopper into the gun body. U.S. Pat. No. 5,947,100 and U.S. Pat. No. 6,415,781 disclose techniques for stirring the contents in a hopper.
However, electric air guns using a motor to fire off bullets require a large number of gears. A large number of gears complicates the structure of a gun and increases its manufacturing cost. Especially, fully automatic electric air guns repeat complicated action in a short time to fire off a large amount of bullets and thus frequently become faulty. For this reason, fully automatic electric air guns are inferior in endurance. In a fully automatic electric air gun, a piston frequently jets out compressed gas and the firing pressure of compressed gas is low.
Consideration will be given to an air gun so configured as to use a solenoid to move a valve to jet compressed gas out of an air chamber without use of a motor. In this case, the inexpensive solenoid does not bring pressing force sufficient to open the valve. A solenoid that can bring sufficient pressing force is more expensive than motors and increases the manufacturing cost of a gun.
Further, consideration will be given to an electric air gun so configured as to transmit the rotary power of a motor through a large number of gears. In this case, switching between single firing and repetitive firing is mechanically carried out. For this reason, it is difficult to limit a number of times of firing and arbitrarily change a limited number of times of firing.